It has long been recognized that the addition of a small amount of certain oxirane compounds to polycarbonate compositions significantly increases their hydrolytic stability. The prior art is noted to include U.S. Pat. No. 3,489,716 which discloses certain epoxidzed cycloaliphatic compounds as heat and color stabilizers for polycarbonate compositions. U.S. Pat. No. 3,839,247 discloses a water clear hydrolytically stable polycarbonate composition which contains aliphatic or aromatic epoxides. This document explicitly teaches away from using cycloaliphatic epoxides which it characterizes as unsuitable since they result in haziness after steam autoclaving.
Also noted in U.S. Pat. No. 3,978,020 which discloses an epoxide as a co-additive with a phosphonite in the context of a thermally stable or polycarbonate composition. Also noted in the prior art is U.S. Pat. No. 3,634,312 which discloses thermally stable polycarbonate compositions which contain a mixture of a copolycarbonate/phosphite with any of a great number of epoxides.